Three more new cars broke cover on Tuesday ahead of the opening day of pre-season testing at Valencia.
Williams' FW33, featuring a KERS system designed by the famous team, is painted in interim navy-blue colours ahead of a livery launch at a later date.
It was debuted by Rubens Barrichello shortly after the pitlane opened at 10am. Pastor Maldonado, whose sponsor PDVSA is one of only a few decals on the pre-launch car, will follow on Wednesday.
"We're optimistic. We think this is a good car," said technical director Sam Michael.
Also launched early on Tuesday was the new Mercedes W02, painted in a striking new shinier silver and visibly very different to last year's car.
"The new Silver Arrow has little in common with its immediate predecessor," confirmed Norbert Haug, referring to the 2011 machine that will be debuted by Nico Rosberg.
Another car launched on Tuesday was Toro Rosso's STR6, but it was Fernando Alonso in Ferrari's new F150 with the fastest installation lap so far.